Jewelry Applications Research Articles

Fabrication of Ruby by 3D printing of transparent salt solutions

A novel method is presented for fabricating 3D-printed Cr3+-doped α-Al2O3 complex structures, known as Ruby, using digital light processing (DLP) 3D printing and sol-gel reactions based on solutions only. The aqueous printing solution comprises aluminum and chromium chloride as the sol-gel precursor and acrylic acid (AA) as the polymerizable component. After photopolymerization, aging, and sintering at 1150°C, structures shrink up to 28±7 %, achieving a final printing resolution of 55.7±0.7 μm, surpassing the nominal printer’s resolution of 200 μm. Characterization includes X-ray diffraction, scanning electron microscopy, UV-Vis, and fluorescence measurements, revealing crystalline Cr:α-Al2O3 composition emitting at 693 nm. The structures exhibit maximum compression stress of 89±3 MPa and microhardness of 340–500 HV, showcasing potential applications in thermal insulation, jewelry, and mechanical uses.

Exploring and Proposing Appropriate Provisions Addressing the Mineral Resources Subjects and Governing Entities within the Framework of Gemological Law of Ukraine

Under this study, an interdisciplinary classification is developed concerning the entities of the gemological law. The classification is grounded in a symbiosis of criteria that define the content and scope of responsibilities, type of gemological activity undertaken, and the condition and appearance of a gemological object. The classification holds practical applications in mining, jewelry, business and management. Additionally, it can be employed in academic studies focusing on theoretic advancements in gemology, mineralogy, geology and jurisprudence. Introduction of this classification into the current legislation would enable both the entities of gemological law and law enforcement to integrally understand the spectrum, possibilities, forms and means of fulfilling their interests, along with their interrelations with other stakeholders. This research underscores that the primary criterion for developing an interdisciplinary classification of gemological law subjects is the type of gemological activity. Its symbiosis with other criteria, determining an entity’s responsibilities, as well as the condition and appearance of objects, establishes a practically reasonable and scientifically substantiated approach to the perception and understanding of this branch of gemological law. To propose to classify the entities of gemological law, three criteria may be: 1) content and scope of duties; 2) type of gemological activity; and 3) condition and appearance of a gemological object. It is important to note that this classification cannot and should not have strict limits, as entities of gemological relations exhibit inter-group features that manifest in general, group-classified, and direct levels of connections between administrative, mining, and economic relations. The dynamics within these relations can reflect the development and change of one kind of relation to another, along with the accompanying relations.

Study on Technical Parameters and Suitability of Platinum-Based Metallic Glasses for Jewellery Applications

Jewellery-specific standardised tests as well as bulk metallic glass (BMG)-specific testing methods were performed on a series of platinum-based BMGs with and without phosphorus, to evaluate their suitability as jewellery items. Their mechanical properties (elasticity, Young’s modulus and yield stress) were determined by three-point beam bending measurements. Hardness, wear and corrosion resistance were tested in comparison to state-of-the-art crystalline platinum-based jewellery alloys. The platinum-BMG alloys exhibit elastic elongation of about 2%. Compared to conventional crystalline platinum-alloys, their fracture strength of ca. 2 GPa and their hardness of ca. 450 HV1 is four and two times higher, respectively. However, the BMGs show less abrasion resistance in the pin-on-disc test than the conventional benchmark alloys due to adhesive wear and microcracking. Regarding the corrosion resistance in simulated body fluids, the BMG alloys reveal a slightly higher release of metals, while the tarnishing behaviour is comparable to the benchmark alloys. The phosphorus-free platinum-BMG alloy showed pronounced tarnishing during exposure to air at elevated temperature. The outstanding thermoplastic formability, a special feature of amorphous metals that can be crucial for enabling novel and filigree designs, was determined and quantified for all BMG alloys.

Effect of equal-channel angular pressing on ordering kinetics and twinning in an 18-carat AuCuAg alloy

The ability to modify microstructural features and the resulting properties of red gold provides an attractive potential for applications in electronics, dental devices or jewelry. In this study, the effect of severe plastic deformation by equal-channel angular pressing (ECAP) on microstructural evolution in an 18-carat AuCuAg alloy, and on the ordering kinetics during subsequent aging, is investigated. Differential scanning calorimetry measurements show that the ordering process is significantly influenced by a plastically deformed microstructure and lattice defects introduced by one or two passes of ECAP. Electron backscatter diffraction and transmission electron microscopy demonstrate that the microstructural evolution during ordering, accompanied by the formation of an L10 superstructure, substantially depends on the thermo-(mechanical) history of the material: While the undeformed material clearly shows a hierarchical structure of twins on different length scales, only a few nanotwins are observed within the strongly deformed microstructures after ECAP. Moreover, after ECAP, static recrystallization is considerably suppressed during long-term annealing at elevated temperatures close to the phase transition temperature. These results clearly highlight the potential of ECAP in combination with heat treatments for microstructural optimization of AuCuAg alloys and their applications.

Development of glass-ceramics from Soda lime silica glass waste with addition of kaolin and coloring oxide for Turquoise’s imitation

Turquoise, a hydrated phosphate of copper and aluminum, is an opaque, blue-to-green mineral with the chemical formula CuAl6(PO4)4(OH)80.4 H2O. Owing to its unique hue, turquoise is rare and valuable, and it has been appraised as a gemstone for thousands of years. However, with high porosity, low specific gravity, fracturable, and low hardness of just under six or slightly more than window glass, treatments are required before use as jewelry. Nowadays, imitations, and synthetics from glass, plastic, or pressed turquoise powder bonded with resin, are generally found in the market. In our present study, we aim to investigate an alternative method to form glass-ceramic for turquoise imitation by using a direct sintering method based on the soda-lime-silica glass waste with kaolin mixer and coloring oxide additives. In the preparation, the pre-mixed powders were poured into a stainless-steel die, then, the die was brought to the pressing machine for sample forming. A conventional furnace was applied for heating the samples to ∼1000 °C with a soaking time of 4 h. The obtained ingots were characterized by several techniques. The chemical compositions were determined by the Energy Dispersive X-ray Fluorescence (ED-XRF), and their chemical structures were evaluated by the X-ray diffractometer. Meanwhile, their chemical fingerprints were obtained by Raman spectroscopy. As for comparison, the natural turquoise, as well as the commercial imitation samples, selected from the local market were undergone the same characterization. We have found that with the proper content of the metal oxide additives, the products in unique blue and brown-turquoise appearances can be formed and cut to decorate the jewelry set for the niche market. Thus, an alternative method for recycling soda lime-silica waste glass based on a single-step sintering process at relatively low temperature enabled jewelry applications.

Mapping Spatial Distribution of Pores in an Additively Manufactured Gold Alloy Using Neutron Microtomography

A crucial criterion for the quality of the additively manufactured parts is the porosity content for achieving an acceptable final relative density. In addition, for jewelry applications, visible pores are unacceptable at or in the vicinity of the surface. In this study, non-destructive 3D neutron microtomography is applied to map the spatial distribution of pores in additively manufactured red-gold samples. The 3D imaging assessment underlines the high relative density of the printed red-gold sample and indicates residual pore sizes are predominantly below the limit of concern for jewelry applications. The 3D maps of pores within printed samples highlight the effect of the scanning strategy on the final quality and location of pores in the printed samples. These results confirm that neutron microtomography is a novel and precise tool to characterize residual porosity in additively manufactured gold alloys and other higher-Z materials where such investigation using other non-destructive methods (such as X-rays) is challenging due to the limited penetration depth.

Thermoplastic forming of additively manufactured Zr-based bulk metallic glass: A processing route for surface finishing of complex structures

Additive manufacturing of bulk metallic glasses (BMGs) through laser powder bed fusion (LPBF) has drawn growing interest in the last years, especially concerning industry-relevant alloys based on iron or zirconium. The process-inherent high cooling rates and localized melting pools allow to overcome geometrical restrictions given for the production of BMGs by classical casting routes. Yet, the achievable surface qualities are still limited, making an adequate post-processing necessary. In this work, we report on applying thermoplastic forming on LPBF-formed parts for the first time to decrease surface roughness and imprint finely structured surface patterns without the need for complex abrasive machining. This BMG-specific post-processing approach allows to functionalize surface areas on highly complex LPBF-formed specimens, which could be of interest especially for medical or jewelry applications.

Evaluation of the kinetics of gold biosorption processes and consequent biogenic synthesis of AuNPs mediated by the fungus Trichoderma harzianum

Gold has several applications in electronic equipment, jewelry, catalysts, and nanoscale, emphasizing the biomedical field. Some conventional effluent treatment methods are used in gold recoveries, such as electrochemical treatments, reverse osmosis, and ion exchange resins. However, these technologies have disadvantages, such as high cost and toxicity. Biosorption appears as a low cost and environmentally friendly alternative. Studies have shown that many biosorbents also synthesize biologically metallic ions into nanoparticles from reduction, nucleation, and subsequent stabilization. This work aims to evaluate gold’s biosorption utilizing fungal biomass of Trichoderma harzianum , promoting nanoparticles’ biogenic synthesis simultaneously. The results showed that 0.4 g L −1 of fungal biomass added the gold ion solution to 400 mg L −1 is possible to perform the processes of biosorption (metal removal) and biogenic synthesis of gold nanoparticles from 30 min under agitation simultaneously. The fungus T. harzianum has a high biosorbing gold capacity, approximately 1340 mg of the metal per g of biomass in 180 min, and a removal rate above 60%. The gold biosorption mediated by T. harzianum was adjusted to the kinetic pseudo-second-order (PSO) model, with R 2 of 0.99 and biosorption capacity calculated according to this model 1342.93 mg g −1 . The biosynthesized nanoparticles had a nanometric size distribution below 30 nanometers and spherical shape. • The fungus Trichoderma harzianum can carry out the processes biosorption of gold and biosynthesize AuNPs. • The fungal biomass showed a biosorption capacity of 1340 mg g −1 and removal rate of 62%. • The biosorption profile was adjusted to the kinetic model of PSO. • T. harzianum synthesized AuNPs biologically with an average size of 15 nm and spherical shape. • 95% of the biosynthesized nanoparticles had a diameter of fewer than 30 nanometers.

High-resolution large-scale plasmonic laser color printing for jewelry applications.

We offer to use optical features of surface plasmon resonance in Ag nanoparticles for jewelry application as a method for the well-controlled decoration of silver items. The novel approach of silver nanoparticles formation with sizes from 5 to 50 nm via nanosecond direct laser writing allows for controlling the reflectance spectra, thus creating a color image on precious metals with a high resolution of about 450 dpi without dyes or hazardous chemicals. Moreover, the large-scale color image can be applied in single-step processing with significant productivity of 2 cm2 per minute. This work opens a strong direction for the practical application in the jewelry industry, art, and coining.

Development of Glass-Ceramics from Soda Lime Silica Glass Waste by Direct Sintering Method for Opal Imitation

Natural opal, an amorphous, hydrous form of silica (SiO2-n-H2O), has been one of the favored precious gemstones for many centuries. Though beautiful, opal is very fragile and is damaged quite easily. Thus, opals of all varieties have been synthesized experimentally and commercially. The objective of this project was to synthesize and to compare crystalline opals. In this work, the development of powder sintered glass ceramics process based on soda lime silica glass waste with metal oxide powder enable jewelry applications. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low temperatures (900–1,000°C), whereas glass/metal powder interactions resulted in the formation of color agent crystals, provide enhancing optical properties. Several techniques were applied for characterization of the ingots. The chemical analysis was performed by Energy Dispersive X-ray Fluorescence (ED-XRF). The mineralogical compositions of the samples were determined by X-ray diffraction analysis. Raman spectroscopy was applied for optical characterization. The results were compared with a natural common opal. The present investigation demonstrated that the common opal with both color and colorless appearance can be synthesized by the technique, as the crystalline phase of opal structure was identified by XRD measurement. There is a great potential for such materials with novel functionalities for artificial gemstone application, i.e. opal forming.

New perspectives for recycling dental zirconia waste resulting from CAD/CAM manufacturing process

On modern prosthodontics, CAD/CAM technology is the main manufacturing technique to produce the all-ceramic restorations. Zirconia stabilized with 3%mol of yttria (3Y-TSZ) is the most used material in the production of dental prostheses (e.g. crowns), due to its high biocompatibility, high mechanical strength, oxidation and abrasion resistance, high hardness and fracture toughness. The machining of crowns can produce a waste of approximately 30% of the initial blank, generating a significant economic loss (∼US$ 1087/kg) for the prosthetic laboratories.This work describes the beneficiation of zirconia powder resultant from CAD/CAM milling process, and suggests different applications based on the new properties. Is proposed a recycling solution by mixing the residues with commercial powder with 5, 10 and 50 vol% of residues and prepared by dry mixing, then pressed at 100 MPa and sintered at 1500 °C for 2 h. The quality control of the residues included the particle size distribution, the crystalline phases and chemical composition. For the recycled mixtures it was analyzed the color difference, the microstructure and mechanical properties, as Young and Weibull modulus, and flexural strength, to evaluate the potential uses of this new material.These residues can be used without any additional treatment on applications such as zirconia sand blasting for prosthodontics and as raw material for jewelry, pigment and refractory industries. In the case of the recycled mixtures is suggested the use in jewelry applications, taking advantage of their uniform color and mechanical properties which are similar to hardened noble metals alloys.

Analysis of influence factors on part quality in micro-SLA technology

Stereolithography (SLA) is one of the most widely known technologies in the scope of additive manufacturing. It consists in printing layer by layer a photo-polymerizable liquid resin using ultraviolet light. This technology is used for creating models, prototypes and production parts. This paper studies the influence of different parameters in the Micro-SLA (for small scale production) process. The analyzed factors are the resin type, layer height, part orientation and cleaning operations. Our study includes the use of two different resins, widely used in dental and jewelry applications, and the effect of changing the orientation of geometrical primitives in the micro-SLA printing quality.

Development of glass-ceramics from soda lime silica glass waste by sintering method for opal imitation

Natural opal, an amorphous, hydrous form of silica (SiO2-n-H2O), has been one of the favored precious gemstones for many centuries. Though beautiful, opal is very fragile and is damaged quite easily. Thus, opals of all varieties have been synthesized experimentally and commercially. The objective of this project was to synthesize and to compare crystalline opals. In this work, the development of powder sintered glass ceramics process based on soda-lime-silica glass waste with silica powder enable jewelry applications. The substantial viscous flow of the glass led to dense products for rapid treatments at relatively low temperatures (900–1,000°C), whereas glass/metal powder interactions resulted in the formation of color agent crystals, provide enhancing optical properties. There is a great potential for such materials with novel functionalities for artificial gemstone application, i.e. opal forming. Several techniques were applied for characterizing the ingots. The chemical analysis was performed by Energy Dispersive X-ray Fluorescence (ED-XRF). The mineralogical compositions of the samples were determined by X-ray diffraction analysis. Raman spectroscopy was applied for optical characterization. The results were compared with a natural common opal. The present experiments demonstrated that the common milky opal can be synthesized by the technique, as the crystalline phase of opal structure was identified by XRD measurement.

Immersion Corrosion of Sn-Ag and Sn-Bi Alloys as Successors to Sn-Pb Alloy with Electronic and Jewelry Applications

A comparative investigation on the degradation in two distinctive corrosive media (NaCl and ethanol) of Sn-2 wt% Ag, Sn-10 wt% Bi, and Sn-22 wt% Pb alloys and the traditional Sn-40 wt% Pb alloys is performed. The deterioration is represented by both weight variation and corrosion rate in both 0.9% NaCl solution and anhydrous ethanol. It is shown that both uncoated and gold-plated samples are more susceptible to deterioration in NaCl than ethanol medium. A mechanical-to-corrosion (M/C) ratio is determined for each examined alloy. Considering the relative weights and costs associated with both M/C ratio and environmentally-friendly aspects, the Sn-Bi alloy is a potential successor for the traditional Sn-Pb alloys.

Optical absorption and luminescence studies of fast neutron-irradiated complex oxides for jewellery applications

We studied the optical absorption and luminescence of agate (SiO2), topaz (Al2[SiO4](F,OH)2), beryl (Be3Al2Si6O18), and prehnite (Ca2Al(AlSi3O10)(OH)2) doped with different concentrations of transition metal ions and exposed to fast neutron irradiation. The exchange interaction between the impurity ions and the defects arising under neutron irradiation causes additional absorption as well as bands' broadening in the crystals. These experimental results allow us to suggest the method for obtaining new radiation-defect induced jewellery colors of minerals due to neutron irradiation.

A reaction study of sulfur vapor with silver and silver–indium solid solution as a tarnishing test method

It is well known that pure silver (Ag) or sterling silver can easily get tarnished under ordinary atmosphere by sulfur-containing gases. Over past several decades, the industries have tried to formulate and produce silver-based materials that do not get tarnished for various applications including electronics, optics, jewelry, and silverware. Recently, our group has grown silver and silver–indium solid solution ingots and studied their anti-tarnishing property. Since there are no standard tarnishing test methods for Ag-based alloys, we have designed and established an accelerated tarnishing experiment using sulfur vapor as the reacting agent. Sulfur vapor, rather than other sulfur-containing gases such as H2S, is chosen because sulfur vapor reacts with silver more easily to form silver sulfide (Ag2S). After ingot growth, disk samples were cut from silver and silver–indium solid solution ingots and examined with X-ray diffraction (XRD) and scanning electron microscope/energy dispersive X-ray spectroscopy (SEM/EDX). Commercially available Argentium silver was also studied for comparison. Disk samples were placed into the sulfur vapor reacting chamber at 120 °C for 15, 30, 45, and 60 min, respectively. The thickness of Ag2S film grown on the samples was measured. The results showed that Ag2S growth rate depends on indium concentration. For example, with 19 at.% In, Ag2S growth rate on silver–indium solid solution is only 4 % of that on pure silver and 7 % of that on Argentium silver. The excellent anti-tarnishing property of silver–indium solid solution should open up new applications in electronics, jewelry, joining, optics, silverware, and welding.

Analysis and modification of natural red spinel by ion beam techniques for jewelry applications

Abstract Natural spinel (MgAl2O4) can be found in several colors resembling corundum, i.e. rubies and sapphires. In particular, spinels with saturated red appearance, called spinel-rubies or balas rubies, are the most appreciated. However, the beautiful rich red spinels are very rare, they can be found in a range of pastel shades blended with either brown, orange or purple. Therefore, the objectives of the present studies are to investigate the origins of the color blending and to improve the optical property of this gemstone by ion beam techniques. Two non-destructive ion beam analysis techniques, i.e., particle induced X-ray emission (PIXE) and iono-luminescence (IL), have been employed for geochemical analysis of the gems. As an alternative method, ion beam treatment using N2-ion was applied for improving optical appearance and color enhancement of the red Burmese (Myanmar) spinel. For each run, samples were implanted at ion energy of 70 keV to a fluence of ~ 1 × 1017 ions/cm2 and subsequently surface cleaning. UV-Vis spectroscopy, Raman spectroscopy and photoluminescence spectroscopy were selected for sample characterization. As for comparison, the spinel samples from the same origin were heated in air and undergone the same measurement. We have found that the color appearance of spinel can be engineered by both techniques. However, the heating has transformed the normal or the ordered spinel to the inverse or the disordered one, and thus disorder might be used as criteria to determine if the stone has been heated. On the other hand, the crystalline structure of the spinel remains almost the same or slightly disordered after ion implantation. This finding leads to future applications for jewelry.

Influence of crystallinity on thermo-process ability and mechanical properties in a Au-based bulk metallic glass

The present investigation addresses the impact of crystallinity on the mechanical properties: hardness (HV) and toughness (KIC) in an Au49Cu26.9Ag5.5Pd2.3Si16.3 BMG which appears especially attractive for applications in jewelry and watch making industries. Thermal stability is first determined using differential scanning calorimetry (DSC), X-ray diffraction and thermo-mechanical analysis (TMA). Then the conditions (time, temperature) in which crystallization is observed (during annealing above the glass transition temperature) and the kinetics are determined. Results show an increase of hardness proportional to the volume fraction of the crystalline phase (ϕ) (from about 350 HV up to about 480 HV), and a drastic reduction in fracture toughness from about 20MPa√m down to 1.5MPa√m for fully crystalline structure. Finally the conditions required achieving a good compromise between hardness and toughness are established.

Tripling hardness of gold by micro alloying coupled with cold processing

Gold has broad applications in jewelry, but suffers from low hardness. In the present work, we show that simultaneous addition of 0.1 wt.% Ce and Si can nearly double the hardness of fine gold. We further show that hardness can be tripled by subsequent cold processing. By systematic structural characterizations and thermal analysis, we find that Ce and Si tend to segregate to grain boundaries and impede grain growth. Our work is helpful for development of new gold micro alloys and for design of jewelry that is more wear and scratch resistant.

Robust anodic colouring of titanium: Effect of electrolyte and colour durability

An ever growing number of studies involve the production of thin metal oxide films for various purposes, from surface hardening to sensing, to the production of self-cleaning surfaces. Among metallic oxides, titanium dioxide is by far the most investigated: it can be produced by anodic oxidation of titanium in a large variety of electrolytes, either acid, alkaline, or neutral, and within certain limits oxide thickness is linearly proportional to the cell voltage applied. Common industrial plants for titanium anodising use acid electrolytes, which may pose safety issues as well as plant corrosion issues. This article proposes a screening of most common, plus some uncommon, electrolytic solutions used in the anodising of titanium, in order to identify suitable alternatives to acids in the range of neutral electrolytes. Oxides produced in optimal conditions are fully characterised, and treatment robustness is investigated, in order to understand the feasibility of technological transfer. A selection of anodising electrolytes and conditions is finally proposed for applications in architectural and jewellery applications, together with a method for colour restoration in case of wear or mechanical damaging.